1. Technical Field
The present disclosure relates to cathode electrodes and lithium ion batteries.
2. Description of Related Art
Polyacrylonitrile (PAN) is a high polymer composed of saturated carbon skeleton containing cyano groups on alternate carbon atoms. PAN itself is not conductive but can be sulfurized to form sulfurized polyacrylonitrile which is conductive and chemically active. Specifically, the PAN powder and sulfur powder are mixed to form a mixture. The mixture is then heated, thereby forming sulfurized polyacrylonitrile. The sulfurized polyacrylonitrile can be used as a cathode active material of a lithium ion battery and has a high discharge capacity at the first cycle.
However, as the cycling of the lithium ion battery continues, the discharge capacity of the lithium ion battery decreases dramatically, which induces a relatively low capacity retention of the lithium ion battery. As reported, the discharge capacity of the lithium ion battery decreases from 906.4 mAh at the first cycle to 740.0 mAh at the 20th cycle. The capacity retention of the lithium ion battery after 20 cycles is only about 81.7%.
What is needed, therefore, is to provide a lithium ion battery using sulfurized polyacrylonitrile as the cathode active material, which has a relatively high capacity retention.